Method of electrolysis with a flowing mercury cathode in a chlorine cell

ABSTRACT

A METHOD OF ELECTROLYSIS WITH A FLOWING-MERCURY CATHODE IN A CHLORINE CELL OF THE HORIZONTAL OR SLIGHTLY INCLINED TYPED WITH TRANSVERSE SECTIONAL PARTITIONS STOPPING SHORT OF THE CELL BOTTOM, WHEREIN ELECTROLYSIS IS CARRIED OUT AT PRESSURE VARYING FROM SECTION TO SECTION, SUCH PRESSURE INCREASING IN THE DIRECTION OPPOSITE TO THE MOVEMENT OF THE MERCURY AND ELECTROLYTE.

I. VOLKOV Filed Aug. 26, 1969 v NQ Feb. 29, 1972 METHOD OF ELECTROLYSIS WITH A FLOWING MERCURY cA'monm IN A CHLORINE can C QI ' US. Cl. 204-99 United States Patent 3,645,866 METHOD OF ELECTROLYSIS WITH A FLOWING MERCURY CATHODE IN A CHLORINE CELL Georgy Ivanovich Volkov, Ulitsa Melnikova 23, kv. 11,

Moscow, U.S.S.R.

Filed Aug. 26, 1969, Ser. No. 853,063

Int. Cl. C01d 1/08 4 Claims ABSTRACT OF THE DISCLOSURE A method of electrolysis with a flowing-mercury cathode in a chlorine cell of the horizontal or slightly inclined type with transverse sectional partitions stopping short of the cell bottom, wherein electrolysis is carried out at pressure varying from section to section, such pressure increasing in the direction opposite to the movement of the mercury and electrolyte.

The present invention relates to the production of chlorine by means of a mercury-cathode electrolysis method Solutions of metal chlorides forming amalgams with mercury, such as alkaline metal chlorides and alkaline earth metal chlorides, can be subjected to electrolysis.

Known in the art is a method of electrolysis in horizontal or slightly inclined cells with transverse sectional partitions stopping short of the bottom of the cell. With this arrangement the pressure in each of the cell sections is maintained at the same level due to free flowing of chlorine from section to section or collecting the chlorine in a common receptacle. Such cell-s are made sectionalized to allow opening of individual separate sections to replace anodes or to clean cathodes without interrupting the process.

A disadvantage of the known electrolysis methods carried out in sectionalized as well as non-sectionalized cells is that with only a slight inclination of the cell, the velocity of the electrolyte flowing through the cell is insufficient. It is difficult to provide a greater degree of inclination for constructional reasons. The impossibility of effecting a considerable increase of the electrolyte velocity does not allow eltective removal of gas bubbles from the anode surface. Due to voltage losses by overcoming the electrolytic resistance in the interelectrode gap, the electrolysis in known methods must be carried out either at a lower current density or increased voltage.

An object of the present invention is to eliminate this disadvantage.

A more specific object of the present invention is to develop a more eflicient and economical method of electrolysis providing the simplest possible way for the electrolyte to flow through the interelectrode gap with a higher velocity.

These objects are attained in a sectionalized electrolytic cell, in which, according to the present invention, electrolysis is carried out under pressure varying from section to section so that the pressure increases in the direction opposite to the movement of the mercury and electrolyte. Pressure varying from section to section produces an additional driving force which permits speeding up the flow of electrolyte in the electrolysis area so that the electrolyte is forced back by the gas and made to pass under partitions dividing the cell into sections. Accelerated movement of the electrolyte makes for the removal of gas bubbles from the anode surface as well as for speeding up the movement of the mercury cathode and making it thinner, and, hence, for lessening the amount of mercury charged into the electrolytic cell.

It is most advisable for the electrolysis to be carried Patented Feb. 29, 1972 out at a pressure drop from 20 to 200 mm. of water column per 1 m. of the cell length.

When electrolysis is conducted in high-output cells in which the sections are connected through outer overflow devices, it is preferable to control pressure in the cell sections by changing the resistance to the flow of chlorine at the outer overflow devices, when the chlorine flows from section to section or into a common receptacle.

A method of the present invention can be effected in a cell shown schematically in the drawing.

An electrolytic cell 1 is divided into sections by transverse partitions -2 stopping short of the bottom of the cell and tightly fitting to the side walls and cover of the cell.

Anodes 3 with current leads 4 are placed within each of the sections of the cell. electrolyte is fed into the cell through a sleeve 5, and mercury is fed through a sleeve 6. The spent electrolyte and chlorine are discharged through a sleeve 7, while the amalgam produced escapes via a gate 8.

Pressure throughout the cell sections can be controlled by means of shut-off devices when chlorine flows out of each section into a common receptacle (not shown in the drawing). It is also possible, as is shown in the drawing, to make chlorine pas-s from section to section through outer overflow devices 9 provided with some suitable control facilities, such as pinchcocks. The maximum pressure created within the sections depends upon the section length. The most favourable result-s are obtained at a pressure drop from 20 to 200 mm. per 1 m. As soon as pressure in a section forces the electrolyte back below the end of the partition, the gas starts passing under the partition and pressure ceases to increase. For low-output cells it is possible to pass all the gas under the section partitions, whereas for high-output cells it is more expedient to pass a greater part of the gas through the outer overflow devices.

For a better understanding of the present invention given below by way of comparison is an example of carrying out electrolysis according to the conventional and the present methods.

EXAMPLE A 3-meter length cell was divided into three sections stopping short of the bottom and leaving a gap of 8 mm. between the lower ends of the partitions and the bottom of the cell. The height of the cell section was 200 mm., the interelectrode gap was 3 mm. With the free flow of chlorine from section to section the cell operated at a current density of 10 ka. per sq. m. and a temperature of C. The brine (electrolyte) with the concentration of 307 g. per 1. of NaCl was fed in the amount of l./hr. per 1 cm. of the cell width, and mercury was fed in the amount of 12 l./hr. per 1 cm. of the cell width. Under these conditions the electrolysis voltage was 4.7 v. and the thickness of the mercury layer was 3 mm.

When pressure in the sections was increased by way of partially shutting off the outer overflow of chlorine from section to section through the overflow devices 9, velocity of the brine movement increased and the mercury layer became thinner. As the mercury layer became thinner, the interelectrode gap changed accordingly, restoring its original length of 3 mm. by lowering the anodes. The results obtained are tabulated in the table.

TABLE Pressure in sections (in the direction of the With a further shutting oil of the outer overflow devices up to their complete closing, chlorine started passing under the dividing partitions, the pressure in the sections, electrolysis voltage and the thickness of the mercury layer remaining unchanged.

While the present invention has been hereinbefore described with respect to a specific embodiment, it will be apparent that numerous modifications and variations are possible Within the spirit and scope of the invention.

Changes, therefore, in the construction and arrangement may be made without departing from the spirit and scope of the invention as disclosed in the appended claims.

What is claimed is:

'1. A method of electrolysis with a flowing mercury cathode in a chlorine cell of the horizontal or slightly inclined type with transverse sectional partitions stopping short of the cell bottom and defining a plurality of sections, the partitions restricting flow of electrolyte between adjacent sections, comprising carrying out electrolysis under pressure varying from section to section, such pressure increasing in the direction opposite to the movement of mercury and electrolyte whereby flow of the electrolyte will be accelerated from section to section.

2. A method as claimed in claim 1, in which electrolysis is carried out at pressure drops from 20 to 200 mm. of water column per 1 m. of the cell length.

3. A method as claimed in claim 1 wherein the successive sections communicate with each other by means of outer overflow devices, and wherein pressure in the sections is controlled by changing the resistance to the flow of chlorine throughthe outer overflow devices when the chlorine passes from section to section.

4. A method as claimed in claim 1 when using a cell with sections communicating through outer overflow devices with a receptacle common for all the sections, in which pressure in the sections is controlled by changing the resistance to the flow of chlorine at the outer overflow devices when it passes to the common receptacle.

References Cited UNITED STATES PATENTS 2,648,630 8/1953 Basilewsky 204-219 WINSTON A. DOUGLAS, Primary Examiner H. A. FEELEY, Assistant Examiner US. Cl. X.R. 204-219 

